Use of four-wave mixing in optical fibers for applications in transparent optical networks

One of many fiber nonlinear effects is a four-wave mixing (FWM) phenomenon that is resonant when the phase matching condition is satisfied. It only occurs for particular combinations of fiber dispersion and signal frequencies. In particular, phase matching is achieved for signals with very similar frequencies propagating near the zero dispersion wavelength of the fiber. The FWM is a very unpleasant transmission phenomenon in a transparent optical network, but it could be used for building all-optical devices such as wavelength converters, parametric amplifiers, optical demultiplexers, chromatic dispersion compensators, as well as signal to noise regenerators. At the process of device optimization or network planning it is important to know the fiber nonlinear coefficient (NLC). This measurement can be efficiently taken by the observation of FWM in a particular optical fiber. Besides fiber NLC measurement, FWM also enables the measurement of some other important fiber parameters, such as zero dispersion wavelength, chromatic dispersion and polarisation mode dispersion.